Railway traffic controlling apparatus



2 Sheets-Sheet 1 INVENTOR [ha] /V/k/Pfz liflJ ATTORNEY A mw MNM iT,

Nov. 7, 1944. P. N. MARTIN RAILWAY TRAFFIC CONTROLLING APPARTUS Filed June 10, 1943 NSR@ S j LII Nov. 7, 1944. P. N. MARTIN l 2,362,212

:RAILWAY TRAFFIC CONTROLLING APPARATUS INVENTOR l HIJ ATTORNEY Patented Nov. 7, 1944 RAILWAY TRAFFIC CONTROLLING APPARATUS Paul ,.N. Martin, `Penn Township, Allegheny County, Pa., assignor to The Union Switch &

Signal Company, Swissvale, Pa.,

of Pennsylvania a corporation Application June `1l), 1943, Serial No. 490,251

15 Claims.

My'invention Vrelates to'railway trafc-contro1 ling-apparatus, andmore particularly to such apparatususing coded energy.

'Railway traic controlling apparatus, such as, for example, cab 'signal apparatus, using coded alternating track `circuit Current of commercial frequency may be falsely operated by stray currents from nearby commercial power lines. As a rule, lsuch stray or foreign current flows through the rails in multiple, "although the current may not Vbe equal inthe two rails. When such foreign current is present, unwanted energy is picked up by the train carried receivers and it becomes necessary vfor the equipment ltoI distinguish between` the usual control current and the "foreign current even though the two are of the same frequency. The foreign current owing partly in each rail, will vordinarily keep the same phase relation for the two portions of the current, or at least will `not reverse the phase relation of these two portions at any periodic or code rate even though 4such 4current may be Varied as to its magnitude :by action of the trucks yof a train successively spanning the insulated rail joints of i adjoining trackv circuits or some similar `condition. i

Accordingly, an object Vof 'my invention is the provision of improved railway traic controlling apparatus using lcoded energy.

Another object of my invention is the provision of improved lrailway cab signal `apparatus that is not subject to false operation by induced current from nearby power linesfof the same frequency .as the cab :signal 'control current.

Again.1 "an, object of my invention is kthe provision of improved cab signal apparatus that makes use of codes that offer immunity to foreign rail currentof the same frequency as the coded track circuit current by which the cab signals are controlled. -i

`Sti-ll another feature oi :my `invention isy the provision of cab signal apparatus that yoffers imrepeated at a predetermined code rate. Furthermore, I provide pole changing means for suchv trackway apparatus to reverse the phase of the current relatively to the source of supply upon the occurrence of each successive on code period. In other words, the current is coded to have a predetermined code rate and the current pulses of successive on code periods to be of reverse relative polarity. The train is provided with two inductors mounted ahead of the leading pair of wheels with one inductor over each rail for each inductor to receive an electromotive force in response to the track circuit current. The two inductors are alike so that the electromotive `forces are of substantially the same magnitude, have a given phase relationship and each isy of a code pattern that corresponds to that ofthe rail current. These two electromotive forces are used to excite a trainl carried two element two position master relay. The two electromotive forces of the two inductors are irst fed into two trans'- formers, each of which 'is provided with two primary windings and a preselected one of which has two secondary windings. Each inductor and a primary winding of each transformer are connected in series. The two primary windings of the preselected one ofthe transformers are additive with respect to the electromotive forces received by the inductors due to the track circuit current flowing in the rails `in series, and the primary windings of the other transformer are opposed to each other with respect to such received electromotive forces. Conversely, the primary lwindings of the preselected transformer are opposed and the primary windings of the other transformer are additive in respect to electromotive forces received by the inductors due to foreign. current flowing in the rails in multiple. The control electromotive force created in a rst one of the two secondary windings of the preselected transformer is applied to a rst one of the elements of the master relay through an amplifier to excite that element, and the electromotive force createdin the second one of the two secondary windings of the preselected'transformer isI applied to a second one of the relay elements through a secondary winding of the other transformer and an` amplifier to excite that element. These two electromotive forces created in the two secondary windings of the preselected transformer have a given phase relation and the relative polarity oi each is reversed each on code period of the rail current due to the phase reversal of the rail current upon the occurrence of each on code period and the master relay would Ibe oper- `ated to one position only unless there is a reversal on the train of the electromotive force applied to one of the relay elements each on code period. I provide the train carried apparatus with phase inverting or pole changing means in the connection of the second relay element and which means is operated each on code period. In this way the electromotive force applied to this second relay element is always of the same relative polarity and the relay is alternately operated to lits two positions because of the reversal of the relative polarity of the electromotive force applied to the first relay element due to the phase reversal of the rail current. Consequently, the master relay is operated at a rate corresponding to the code rate of the rail current.

Furthermore, I provide the train carried apparatus with a group of relays controlled jointly by the electromotive force picked up from the rails and by the position of the master relay to synchronize the pole changing of the connection for the second element of the master relay with the on code period of the rail current, and the pole changing of the trackway apparatus and of the train carried apparatus are kept in step.

Such phase reversal of the rail current each on code period together with the special arrangement of the train carried transformer windings substantially removes all possibility of operation of the master relay due to foreign rail current even when such foreign current is of the same frequency as that of the cab signal control current.

I shall describe three forms of apparatus embodying my invention, and shall then point out the novel features thereof in claims.

In the accompanying drawings, Fig. l is a diagrammatic view showing one form of trackway and train carried apparatus embodying my invention.. Figs. 2 and 3 are diagrammatic views showing two different forms of` trackway apparatus each of which may be used with the train carried apparatus of Fig. 1, and each of which also embodies my invention. Fig. 4 is a view showing diagrams of the code patterns of the track circuit current effected by the trackway apparatus of Figs. 1, 2 and 3.

In the different views, like reference characters are used to designate similar parts.

Referring to Fig. l, the reference characters Ia and Ib designate the track rails of a stretch of railway track and which rails are formed by the usual insulated rail joints with consecutive track sections for a signal system, only the one section D-E and the adjoining ends of the two adjacent sections are shown, however, because these are suflicient to illustrate ythe invention. Each track section is provided with a track circuit including a current source connected across the rails at the exit end of the section and a track relay connected across the rails at the entrance end of the section. The track relay of one section controls the current source of the section next in the rear, and each track circuit is responsive to'traic conditions in advance of thea respective section as well as to traiiic conditions of the respective section. Consequently, as the junction location of two sections, a portion of the trackway apparatus is associated with the section next in advance of such location, and a portion is associated with the section next in the rear of such location. The apparatus at all such locations would be substantially alike, and a description of the apparatus at one such location is suicient for an understanding of all. Y In Fig.

1, the apparatus at location E is shown complete, while that at location D is only shown in part for the sake of simplicity, and it is to be understood that location D of Fig. l and all similar locations are provided with apparatus that is substantially a duplication of that of location E.

Referring to location E of Fig. 1, the immediate current source for the track section D-E is a track transformer TE, the secondary winding 2 of which is connected across the rails of the section at the exit end thereof, and the primary winding 3 of which is supplied with alternating current in a manner to appear shortly. The track relay for section D-E is a direct current relay DTR connected across the rails at location D through a transformer-rectifier unit RQ which rectifies the alternating current supplied to the rails through transformer TE, the unit RQ being shown conventionally since its structure is wellknown and forms no part of my invention. Consequently, when section D-E is unoccupied, thatv is, when a train shown conventionally at TN is not present, track relay DTR is energized and picked up whenever alternating current is supplied to the rails through transformer TE and the relay is deenergized and released whenever such rail current is interrupted. In other words, relay DTR is operated at the code rate of the alternating current supplied to the track circuit. A track relay ETR for the section next in advance of section D-E is operated by the current supplied to the track circuit of such section in advance in the same manner the track relay DTR is operated by the track circuit current of section D-E.

Operation of track relay ETR at a code rate, such as, for example, 75 or 180 operations per minute, to alternately close its front contact 5 and back contact 6, causes Adirect current from a source the terminals of which are indicated at B and C, to be alternately supplied to the two portions of winding 'I of a decoding transformer DT, with the result that an electromotive force is induced in winding 8 of transformer DT, the frequency of which electromotive force corresponds to the code rate at which relay ETR is operated. Winding 3 is connected to a relay EH through front contact 9 and back contact I l) of relay ETR, and the electromotive force of winding 8 is rectied for energizing relay EH, relay EH being picked up when relay ETR is operated at either the 75 or 180 code rate.

Two code transmitters or coders ISUCT and 15CT are included in the trackway apparatus at location E. The type of such code transmitters is immaterial, and it is sufficient to point out that when current is supplied to an operating winding of a code transmitter, contact members are operated in a cyclic manner at a code rate preselected for the transmitter. Front contacts of such contact members are closed during one-half of each operation cycle to form an on code period, and such contacts are open during the other half of each code cycle to form an off code period. As here shown, the operating winding of code transmitter ICT is supplied with current by an obvious circuit including front contact II of relay EH and its contact members I2, I3 and I4 are cyclically operated at the rate of say times per minute. The operating winding of code transmitter 'I5CT is supplied with current by an obvious circuit including back contact I5 of relay EH and contact members I6, I1 and I8 of this code transmitter are cyclically operated at say 75 times per minute. It is to be underacca-,212

stood, of course, that my inventionis not lim ited to these code rates, and other code rates can beused.

When two different code rates, such as 'T5 and '186' are provided, the code rates would be used to control a wayside signal to diiierent positions, but such way side signal and control mean-s are omitted fromthe drawing for the sake of simplicity since they form no? part` of my invention.

'Jvvo relays FS and BS are operatively associated with the code transmitters to provide a pole changing means, relays FS and BS being operated at half the code rate of the active code transmitter. Assuming that relay EH is picked `up closing front contact III to set coder I80CT into loperation and relays FS and BSl are at the start4 both released, neither relay is energized during an initial on code period of coder IBBCT. At the rst off code period current flows from terminal B through fron-t contact II of relay EH, coder con-tact I 2--I9, back contact20 of relayv BS and winding of relay FS- to terminal C', and relay FS is picked up. At the next and first elective on code period, relay FS is. re-

tained energized by a stick circuit including its own front contact 23 and coder contact I2--2I. Also current ows from terminal B throughfront contact4 II, codercontact I3-22, front contact 26; of rel-ay FS and Winding of relay BS to ter minal C, and relay BS is picked up. At the next and second off code period relay BS is retained energized by a stick circuit including its own front contact 25 and coder contact Iii-I9, but relay FS is now Without current and is immediately released. At the next and second ef- I6 and I1 of code transmitter 15CT` control the` .circuits for relays FS and BS in the same manner that these circuits are governed by contact members I2 and I3 of 4coder I80CT, and hence when relay EH is released closing back Contact f5 to set coder I5CT into operation, the relays FS and BS are cyclically operated at half the code rate of coder 15CT, relay FS being picked up for the` odd' numbered on code periods and beingy released for the eyen numbered on code periods.

Relay FS is provided with pole changing contacts through which current is supplied to transformer TE from a` suitable source of alternating current theterminalsv of which are indicated atV BX and CX, and which source may be of any frequency and may be of the usual commercial frequency of 60v cycles per second. When track relay ETR is.` released as it will lbe when the section next in advance of section D-E is occupied, relayv EH is released closing back contacts I5 and 21. The closing of back contact I5 brings about operation of coder 15CT, and in turn of relays FS and BS are explained above, During an odd numbered on code period,y relay FS is 'l picked up, alternating current ows from termi-A nal BX through front pole changing contact 23 of relay FS, contact I8--29` of coder 15CT, back contact 21 of relay EI-I, primary winding 3 of track transformer TEv and` front pole changing contact 3U Vof relay FS to terminal CX, and alL ternating current of a given relative polarity is supplied to the track circuit of section D-E. During each even numbered on code period, the connection is pole changed at back contacts 3I and 32 of relay FS, and the current supplied to `the track circuit through transformer TE is of the reverse relative polarity. That is, the circuit is pole changed so as to reverse the phase of the current supplied to the track circuit with respect to the BX-CX source upon the occurrence of each on code period. When the section next in advance of` section D-E is unoccupied and `relay ETR is operated, relay EH is pickedup closing front contacts II and 433, the closing of front Contact I I bringing aboutv operation of coder I,8.0CT and of relays FS and BS in the manner already explained. During .an odd numbered onv code period current flows from terminal BX through front Contact 2,8 of relay FS, coder contact III-34, front contact 33 of relay EH, primary winding. 3 of transformer TE and front contact 30 to terminal CX. During each even numbered on code period, relay FS is released and current of reverse relative polarity is supplied -to the primary winding 3 of transformer TE. Hence the track circuit current is now of the 180 code rate and the phase is reversed each on code period. The pattern of such coded current is illustrated by the upper graph of Fig. 4, which will be readily understood by an inf spection of the drawings.

As stated hereinbefore, track relat7 DTR at location D controls the supply of current `to the track circuit of the section next in the rear of section D-E, in the same manner that relay ETR controls the supply of current to the track circuit of section D-E.

A train traversing section D-E is indicated conventionally at TN, train TN having mounted thereon .cab signal apparatus which is effectively l controlled by the coded alternating current supplied to the rails oi the section D-E` by the trackway apparatus at location E. This train carried apparatus includes two inductors 35 and 33 mounted ahead of the leading pair of wheels above rails la and Ib, respectively. These in-v ductcrs are alike and consequently the electromotive forces picked up by the inductors due to this .coded rail current are of substantially the same magnitude, have a given phase relation and each is of the same code pattern as that of the rail current. These inductors are connected to a iirst and a second train carried transformer TI and T2, transformer TI being provided with two` Iprimary windings 3l and 38. and two -secondary windings 39 and 40; and transformer T2 being provided with two primary windings 4I and fi? and a` secondary winding 43. Inductor 315.', primary winding 3l of transformer TI` and winding 4I of transformer T2 are connected in series; and inductor 35 is connected in ,series with primary windings 38 and 42 of transformers Tt and T2, respectively. Primary windings. 3'! and 38 of transformer Ti are disposed transformer Tl but none is induced in secondary winding 43 of transformer T2 in response to the track circuit current.

A master code following relay MF of the train carried apparatus is excited by the electromotive for-ces induced in secondary windings (39. and 40, relay MF being a two element two position alternating current relay. Furthermore, relay MF is characterized by its armature once started from a position the armature moves to the opposite position even though the relay in the meantime becomes deenergized, and also by its armature remaining in the position to which it was 'last moved when the relay is deenergized. A first element 44 of relay MF is connected to secondary winding 39, lpreferably through an amplier AMI of standard construction. A second 'element 45 of relay MF is connected to secondary winding 40 through a similar amplifier AM2, secondary winding 43 oi transformer T2 and contacts of a group of relays A, N and R, as well as contacts of the master relay MF. These amplifier circuits for elements 44 and 45 are arranged to provide the usual phase shift of approximately 90 degrees between the magnetic iluxes set up in the relay MF to operate the relay. To be explicit, a rst connection can be traced from the right-hand terminal of secondary Winding 4D through wire 46, normal contact 41 of relay MF, back contact 48 of relay R,

secondary winding 43 of transformer T2, wire 49, top right-hand input terminal of amplier AM2 to its lower right-hand input terminal, wire 5U, front contacts 5I and 52 of relays A and N, respectively, back contact 53 of relay R, normal contact 54 of relay MF and to the lefthand terminalof secondary winding 40. A second connection can be traced from the righthand terminal of secondary winding 46 through `wire 45, reverse contact 55 of relay MF, back contact 560i relay N, front contact 51 of relay R, front Contact 5I of relay A, wire 50, lower righthand input terminal of amplifier AM2 to its upper right-hand input terminal, wire 49, secondary winding 43, back contact 58 of relay N, and reve'rse contact 59 of relay MF to the left-hand terminal of secondary winding 4U. It is to be noted that the rst traced connection included normal contacts of relay MF and passed from the top to the lower input terminal of amplier AM2 and through the secondary winding 43 from left to right, whereas the second traced connection included reverse contacts of relay MF' and passed from the lower to the top input terminal of the amplier and through secondary winding 43 from right to left. That is to say, the connection of secondary winding 4U to' amplifier AM2 is pole changed lby these two circuit connections, such pole changing being effected each operation of relay MF.

The relays A, N and R serve to synchronize the pole changing action of relay MF with the reversal of the phase of the track circuit current. Relay A is connected to the output side of amplifier AMI preferably in multiple with the element 44 of relay MF, and relay A is energized by a portion of the electromotive force received by the secondary winding 39, with the result that relay A is picked up whenever an electromotive force is received in response to an on code period of they track circuit current and is deenergized and released during each off code period of the track circuit current. The connection of relay A to the output side of amplifier AMI includes a full wave rectiiier 60, back contacts 6I and 62 of relays R and N, respectively, and a resistor 63 which shunts back contacts 6I and 62. The arrangement is such that relay A is picked up only when relays N and R are released and is provided with a release value of current that is substantially as high or higher than the pickup value of current to assure .a quick release of the relay. Relays R and N are in turn governed by relay A according to the position of the master relay MF. With relay A picked up and relay lWF at its normal or right-hand position, current iiows from terminal B through normal contact 64 of relay MF, front contact 65 of relay A, winding of relay N and back contact 66 of relay R to terminal C. Relay N once picked up is retained energized by a stick circuit independent of relay MF and which stick circuit includes front contact 61 of relay N, front contact 65 of relay A and back contact 66 or relay R. Similarly, when relay A is picked up and relay MF occupies its reverse or left-hand position, relay R is selected by current owingfrom terminal B through reverse Contact 68 of relay MF, front contact 69 of relay A, back contact 'Hl of relay N and winding of relay R to terminal C. Relay R is provided with a stick circuit including its own front Contact 1|, front contact 69 of relay A, and back contact 'I0 of relay N. The function of relays A, N and R will appear more fully when the operation of the apparatus is described.

A three position cab signal CS is controlled by the master relay MF according to the code rate at which the master relay is operated. Operation of relay MFto alternately close contacts 'I2 and 'I3 causes direct current to be alternately supplied to the two portions of a primary winding of a decoding transformer of a decoding unit DU of well-known construction and which is shown conventionally for the sake of simplicity. It is suiiicient for this application to point out that operation of relay MF at the code causes decoding unit DU to be energized in a manner that a relay AA is energized to in turn cause a clear lamp 'I4 of cab signal CS to be illuminated. When relay MF is operated at the '75 code rate unit DU is energized in a manner to cause relay AA to be deenergized and a relay LL to be energized and an approach lamp 16 of signal CS to be illuminated, and when relay MF is inactive then the unit DU is conditioned to cause both relays AA and LL to be deenergized and a slow speed lamp 11 of signal CS to be illuminated.

In describing the operation of the apparatus of Fig. 1, I shall assume that the track section next in advance of section D-E is unoccupied and track relay ETR is operated so that track circuit current coded at the 180 code rate is supplied to the section D-E and corresponding electromotive forces are pickedup by inductors 35 and 36 of the train TN causing corresponding electromotive forces to appear in secondary windings 39 and 40 of transformer TI. I shall also assume at first that no foreign current is present. At the start, the electromotive force of secondary winding 39 isamplied and relay A and element 44 of the relay MF are energized thereby. The connection to the element 45 of relay MF is at the start open, and the electromotive force created in secondary Winding 40 is ineffective. Picking up of relay A with relay MF occupying its normal position, selects relay'N, and with relays A and N picked up and relay R released, the first traced connection for secondary winding 4!) is closed causing element 45 of relay MF to be energized. The parts are disposed so that the` phase relation of the electromotive forces applied to elements 44 and 45 of relay MF causes the]` relay to` be operated to its reverse position. Such operation of relay MF opens normal contacts 4l and 54 in the connection by, which element 45l is,4 excited, but `full movement of the armature'l of relay MF to its reverse position is effected because of the characteristics of the relay. At the end of this von code. period, relay Arbecomes dee'nergiz-ed andA immediately releases. At the next oncode period the relay A and the element 44 of relay MF4 are again excited. `Withrelay A picked up, 4and relay MF at .its reverse position, relay R is; selected; and withrelays A and R picked up and relay N released, the second traced circuit con-4 nection `for secondary winding ttly is closed and element 45 of the master relay MF is excited. The phase ofthe rail current of this second on codeA period is lreversed from that of the current of the first on code period and the relative polarity of the electromotive force applied to the rstelement 44 is reversed `but that ap plied to the second element 45 is the same due to thepole-changing of the connection of secondary `winding 40 with the result the phase relation ofl the; electromotive `forces applied to elements 44 and 45 of relay MF is reversed andk the Yrelay is operated -to its normal position. It is to be seentherefore that relay MF is operated at the 180 rcode rate. corresponding to that of therail current, and the cabgsignal lamp 'I4 is illuminated. Since'therst connection for secondary winding 40 includes a front contact oi relay Nanda back contact ofrelay R, and the second connection includes a back contact of relay Nanda front contact of relay R, and since neither relay N nor relay R can-be picked up unless relay A is energized, it follows that pole changing of the connectionof winding 40 can be effected only subsequent to the beginning of an on code period of therail current.

If the section next in advance of section DQE is occupied4 and the track circuit for the section D-'E'is supplied with current of the 75 code rate, the. operation of the train carried -apparatus is the vsame as described above .except that relay MF is operated at arate corresponding to the 75 code rate and lamp IB of signal CS is illuminated. 'kIf another train occupies section D--E ahead of train TN to shunt the track circuit current, then `master relay MF is inactive and the slow-speed lamp Tl Vis illuminated. n

'Electromotiveforces picked up by inductors 35 and 36due to foreign current flowing in the rails of section Del-E in niultiple and of equal Value in each rail will bejbalanced out at transformer Tlbut' a `"corresponding electromotive force will be created in secondary winding 43 of" transformer TZ' due to the' arrangement ofthe windings of the transformers; The foreign electroinotive force of secondary winding 43 will have a component that is in phase or is 180 degrees out of phase withl the control electroinotive force created in secondarywinding 4B of transformer Tl due to the normal track circuit current. If such component is in phase the operationv of the masterrelay` MF is not effected because the pole changing of the connection to the trol electromotive force and is :high enoughVi-t would prevent operation of the master relay for one on code period. On the .next on code period the reversal of the phase of the control electro motive force will bring the two electromotive yforces into phase and operation of the master relay will proceed. The quadrature component of the electromotive force in winding 43 does not produce torque on relay MF because of the proportioning of the degree rphase shifting means included in the amplifier circuits referred to herenbe-fore.

When the foreign current is unequal in the two rails a resultant elect-romotive force is created in secondary Winding '43 of transformer T2 an-d applied to the second -elementl45 of the master relay the same as described above. There is now a resultant foreign eleotromotive force creatediin each of the secondary `windings 39 and 4l! of transformer TI, and if difference between the foreign current in the two rails is large enough such eleotromotive forces might' overcome the control electromotive forces and hold the master relay at one position or the other.. Such action would cause the most ree strictive cab signal H to be displayed. It ap` pears, however,` that with the arrangement here provided it should take a relatively high energy level of foreign current to cause nonoperation` of the master relay.Y

Foreign currents alone would not operate the master relay. If the foreign lcurrent is equal in the two rails, the received electromotive forces are balanced out at transformer TI and the nrst element 44 of the relay MF and relay A 're-' main deenergized. If the foreign current is unbalanced, the .energy appli-ed to 'the rst relay element 44 does not reverse in .phase and would tend to maintain relay A continuously picked up. Even if a variation of the foreign current should occur in some manner, such as, by the train trucks passing or spanning the insulated joints of adjoining sections, the current in the master relay would remain in Vthe saine direction and it would not operate more than once because the electromotive force of Winding 43, 'which depends onA the; sum of the two rail currents, is larger than theV eleetromotive force of winding 40, which depends on the difference betweeny the 'rail currents.

.The apparatus has the advantage of affording improved broken rail protection for' the cab signals. When the train approaches a break in the rail, the difference between the highA current in the good rail and the low current in the broken rail tends to create an electroinotive force" secondary winding 43 of the second transformer T2 and which' electromotiv'e force sets up a polarizing action for the' relay element 45 that vtends to hold` relay MF in one position'.-

Fig. 2 discloses trackway apparatus where alternating current for governing cab signals iS superimposed on av coded direct current track Acircuit. The track circuit for track section D-E of Fig. 2 includes a battery 84 which is coni'iected across the railsr to supply direct current for ener gizing track rel'ay DTR connected to the rails at the entrance end of the section,` relay DTRbeing connected to the rails without the intervening transformer rectifier 'unit of Fig. 1. It follows therefore that` relay DTRv will be energized and picked up whenever direct current from battery 84 is supplied tothe rails and will bereleased Whenever suchcu-rrent is interrupted and isnon responsive to alternating current supplied across `code period of the alternating current.

the rails. Track relay ETR at location E of Fig. 2 is controlled similarly to relay DTR, and relay ETR controls relay EH through decoding transformer DT in the same manner as in Fig. 1. With relay EH picked up closing front contact to bring coder |80CT into operation, a code repeater relay CP for section D-E is operated at the 180 code rate, relay CP being energized by an obvious circuit including contact '|8 of coder |80CT and front contact 'I9 of relay EH. Thus relay CP is energized and picked up during each on code period of coder |80CT and is deenergized and released duringeach 01T code period of the coder. When relay ETR is inactive and relay EH released to bring coder |5CT into operation, then the repeater relay CP is operated at the 75 code rate, the circuit for relay CP including contact 85 of coder '|5CT and back contact 86 of relay EH. Code repeater relay CP is characterized by having a predetermined transfer period for its contacts. That is, when relay CP is energized and picked up a predetermined interval occurs between the opening oi its back contacts 80 and 8| and the closing of the corresponding front contacts 82 and 83. deenergized the same predetermined period is required between the opening of iront contacts 82 and 83 and the closing of the corresponding back contacts 8|] and 8|. During the period relay CP is picked up, track battery. .84 and secondary winding 2 of transformer TE are connected in series across the rails, one terminal of battery 84 being connected to rail Ib through front contact 82 of relay CP anda resistance 8l, and the other terminal of battery 84 being connected to rail Ic through secondary winding 2 and front Contact 83 of relay CP. During each period relay CP is released secondary winding 2 is connected across the rails independent of battery 84, the connections being completed at back contacts 80 and 8| of relay CP. Thus, operation of relay CP causes direct current to be supplied to the rails at a code corresponding to the code rate at which relay CP is operated, and also causes alternating current to be .supplied to the rails, the alternating current being superimposed on the direct current during the period the direct current ilows and being of one relative polarity, and the alternating current being of reverse relative polarity during the oil periods of the direct current. Furthermore, a predetermined off period of the alternating current occurs during each transfer period of the contacts of relay CP. The code pattern of the alternating current for the apparatus of Fig. 2 is illustrated by the lower graph of Fig. 4, and will be readily understood by an inspection of that drawing.

Assuming that the train TN of Fig. 1 with its traincarried apparatus -occupies section D-E of Fig. 2, while the section next in advance is unoccupied and relay CP is operated at the 180 code rate, the alternating current supplied to the rails induces an electromotive force in each of the train inductors and relay MF is operated to its reverse and normal positions in substantially the vsame manner as described in connection with Fig. 1. that is, during the off period of the coded alternating current, relay A of the train carried apparatus is deenergized and released, with the result that the connection for secondary winding 40 of the train carried transformer TI is pole changed and relay MF is operated to its normal or reverse positions at the beginning of each on With Likewise, when relay CP is During the transfer period of relay CP,4

such operation of the master relay MF, the decoding unit DU is energized and lamp 'I4 is illuminated, unit DU of Fig. 2 being proportioned to control indication lamp 14 when relay MF is operated at a rate corresponding to the 180 code rate of the rail current, and to control lamp 'I6 when relay MF is operated at a rate corresponding to the 75 code rate of the rail current.

Fig. 3 shows trackway apparatus Where alternating current for cab signal control is superimposed on coded direct current track circuits using a feed back codeI for approach control. The code repeater relay CPI of Fig. 3 is operated by trackway apparatus for the section next in advance of section D-E in the manner that code repeater relay CP of Fig. 2 is operated, and in a similar manner a code repeater relay CP2 of Fig. 3 is operated by the track apparatus of section D-E for controlling the track circuit for the section next in the rear. Furthermore, each repeater relay CPI and CP2 of Fig. 3 is characterized by a predetermined transfer period for its contacts the same as explained for relay CP of Fig. 2.

It is believed that the apparatus of Fig. 3 can best be understood by a description of its operation. Assuming that repeater relay CPI is being operated at the 180 code rate and it is energized and picked up to close its front contact ||5, direct current flows from battery 88 through front contact ||5 to rail Ib, through rail Ib and wire 89 to a winding of track relay DTRI, normal polar contact 90 of a relay DIR to be later described, wire 9|, rail Ia, wire 92, top portion of secondary winding 93 of a transformer TEI and resistor 94 to battery 88. Track relay DTRI is energized and picked up by this direct current to open its back contact 95 and close its front contact 96. This operation of contacts 95 and 96 causes direct current to be alternately supplied to two portions of primary winding 91 of a decoding transformer TD with the result an electromotive force is induced in secondary windings 98 and 99 of` that transformer. The electromotive force induced in secondary Winding 98 is supplied to a control relay DH through rectifying contacts of relay ETRI, as will be readily understood by an inspection olf Fig. 3. The electromotive force induced in secondary winding 99 is applied to the winding of relay DIR to energize that relay. Relay DIR is a bias polar relay whose armature is biased to the left-hand position as viewed in Fig. 3 when the relay is deenergized and is held in that left-hand position when the relay is energized by current of one polarity and the armature is operated to the right-hand position when the relay is energized by current of the reverse polarity. The connection of secondary winding 99 is such that the electromotive force induced in secondary winding 99 when relay DTRI is dropping outis of the polarity that operates relay DIR to its right-hand position. Such operation of relay DIR disconnects the track relay DTRI and connects battery |00 to the track circuit. Assuming now that during this operation of the relays at location D the repeater relay CPI is released for an 01T code period, current Iiows from battery |00 through wire 89, rail Ib, back contact |0| of relay CPI, Wire |02, unit |03, top winding of a relay RC, Wire 92, rail Ia, Wire 9| and the right-hand polar contact |04 of relay DIR and resistor |05 to battery |00. Relay RC is now operated to close its right-hand contact |06 and complete a simple circuit for supplying foreign Acurrent flowing in the rails in multiple up of relay CPI to close its front contact I I4 completes a simple circuit for energizing the lower winding of relay RC at a polarity that causes its armature to be operated back to its left-hand position, but the approach relay AR remains picked up during the off period because of its slow release characteristic. The above described operation ofthe apparatus of Fig. 3 will continue as long as the section D-Eis unoccupied, With the result thatthe control relay DH at location D and the approach relay AR at location E are energized and picked up. Relay DH is used to control repeater relay CP2, relay CP2 being operated bythe IBUCT coder through front contact H2 of relay DH- and being operated by the 15CT coder through back contact I I3 of relay DH. Ap, proach relay .AR would be used to control any signal desired and in Fig. 3 it is used to control the. supply of alternating current to primary winding HI8k of transformer TEI, current being supplied tothe primary winding through back contact III'I of relay AR.

In the case a train, such as train TN of Fig. 1 withdts cab signal apparatus, enters section D-E of Fig. 3, operation of relay CPI continues but the feed back code current from battery is shunted bythe train and relay RC remains inactive at its left-hand position, causing approach relayrARto be released. The closing of back contact |01 of relay AR to supply alternating current to primary winding I-08 of transformer TEI causes alternating current to be supplied to the I rails by the action of relay CPI, the top half portion of secondary winding 93 of transformer TEI being connected across the rails through front contact. II of relay CPI and the lower half` portion ofvsecondary winding 93 being connected across the rails through back contact IIII of relay CPI. Hence, each period relay CPI is picked up closing front contact II5, alternating current of one relative polarity'is supplied to the rails to ilowin the rails in series, and each period relay CPI is released closing back Contact IIJI, alternating current of the reverse relative polarity is supplied across the rails; also there is an off period for such alternating current durin-g lthe transfer period ofthe contacts of relay CPI.

The unit |03 is a low pass or anti-resonant iilter to Vblock flow of alternating current through the tcp winding ofv relay RC. A high pass or resonantilter consisting of a condenser |09 and an inductance IIU is'interposed in the lead for the `manner as explained in connection with the apparatus of Fig. 2, the alternating current of Fig. 3 having a code pattern as illustrated by the lower-graph'of Fig. 4. n

. yIty `is clear that the train carried apparatus when operated with the trackway apparatus oi either FigJZ .cia3 is .immune to false operation by for the same reasons as described in connection with the trackway apparatus of Fig. l.

It is Vto be seen, therefore, vthat I have provided novel and improved cab signal apparatus that has the advantages of beingsubstantially free `from false operation due to foreign currentthat may be of the same frequency as the frequency of the track circuit current used for controlling the cab signal. v

Although I have herein shown anddescribed only three forms of railway trafc `controlling apparatus embodying my invention, it is understood that various changes and modifications may he made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is: l

l. In combination, a track section, a source of alternating current connected across the rails ofA said section to .supply current thereto, lcoding means having contacts interposed in the connection of said current source to the rails and operable at times to code the alternating current to have alternate on and oii periods of a preselected rate and a reversal of phase with respect to said current `source upon the occurrence of each on period, a train to travelsaid section provided with receiving means mounted .on the train in inductive relation `to the rails to receive `energy in respense to the alternating current thus supplied to the railsand train carried signal apparatus connected to said receiving means and effectively excited by said received energy due to said code rate and reversal of phase of the rail current.

2. In combination, a track section; trackway means including a source of alternating current, a coder and a pole changer; said trackway means connected across the rails of said section to supply such alternating current coded to have recurrent on periods of a preselected code rate and the currents of successive on periods to be of opposite relative polarities with respect to the source of alternating current, a train to travel said section provided with receiving means mounted in inductive relation to the rails to receive energy of a code corresponding to that of the alternating current supplied to the rails, and traincarried signal apparatus connected to said receiving means and controlled by said received energy.

`3. In combination, a track section, trackway apparatus including a source of alternating current connected across the rails of said section to supply thereto an alternating current coded to have recurrent on code periods, a pole changer interposed in said trackway apparatus to reverse the phase of said coded current with respect .to said current source upon the occurrence of each on code period, a ytrain to travel said section, receiving means mounted on the train in inductive relation to the rails to receive energy corresponding in code and phase to that of said rail current, a train carried two-element relay, circuit means to connect the two elements of said relay to said receiving means to excite each said relay element due to said received energy, and pole changing means interposed in said circuit means and controlled by the received energy to reverse the connection oi a preselected one of said relay elements each on `code period of the received energy to operate said relay at a rate corresponding to said recurrent on periods of the rail current.

`li. In combination, Va track section, .a source of train-carried relay alternating current, a coder operable at a preselected code rate, a relay having pole changing contacts and controlled by said coder to operate its pole changing contacts at one half said code rate, means including said pole changing contacts and a contact of said coder to connect said current source across the rails of said section to supply alternating current of said code rate and reversed in phase-with respect to said current source upon the occurrence of each on code period, a train to travel said section and provided with receiving means mounted in inductive relation to the rails to receive energy corresponding in code rate and phase to the rail current, a train carried two-element relay having each of its two elements connected to said receiving means to excite each said element by said received energy, and said two-element relay provided with ypole changing contacts which are included in the connection of a pre-selected one of its elements to said receiving means to operate said two-element relay at said code rate due to said reversal of the phase of the rail current and the pole changingl of the connection to said preselected relay element.

5. In combination, a track section, trackway means including a source of alternating current and a coder and a pole changer and connected across the rails of said section to supply thereto an alternating current coded to have alternate on and off periods and a reversal of phase with respect to said current source upon the occurrence of each on period, a train to travel said section and provided with receiving means mounted on the train in inductive relation to the rails to receive energy corresponding in code and phase to that of said rail current, a train carried ytwoelement alternating current relay, a rst circuit means to connect a rst one of the elements of said relay to said receiving means to energize that element by said received energy, a second circuit means including pole changing contacts of said two-element relay to connect a second one of the elements of said relay to said receiving means to energize said second element by said received energy and operate said relay at said code rate, and train carried relay means connected to said first circuit means to be energized in multiple withsaid first relay element and having contacts interposed in said second circuit means to synchronize the pole changing of said second relay element with the on periods of said rail current.

6. In combination, a track section, trackway means including a source of alternating current and a coder and a pole changer and connected across the rails of said section to supply to the rails an alternating current coded to have alternate on and oif periods and a reversal of phase with respect to said current source upon the occurrence of each on period, a train to travel said section, two inductors mounted on the train one over each rail for each inductor to receive an electromotive force corresponding in code and phase to that of said rail current, a train carried two-element alternating current relay, train carried circuit means including atransformel` to connect each element of said relay to said inductors to energize each said element by energy due to said received electromotive forces, train carried pole changing means having contacts interposed in the connection to a preselected one of said relay elements, and another connected to said circuit means to be energized each on code period of the received electromotive forces to control said pole changing means to cause code operation of said two-element relay due to said phase reversal of said rail current.

7. In combination, a track section having a normal direction of traffic, trackway means including a source of alternating current and a coder and a pole changer and connected across the rails at the exit end of said section to supply alternating current which ows in the rails in series and which is coded to have recurrent on periods with a reversal of phase with respect to said current source upon the occurrence of each on period, a train to travel said section and having two inductors mounted ahead of the leading pair of wheels of the train with one inductor over each rail for each inductor to receive an electromotive force in response to said rail current, a train carried transformer having two primary windings one connected to each of said inductors and disposed to add their effects with respect to said electromotive forces due to said series rail current, a train carried two-element relay, a first circuit means to connect a rst one of the elements of said relay to a first secondary winding of said transformer to excite that element in response to said received electromotive forces, a second circuit means to connect the second one of the elements of said relay to a second secondary windingof said transformer to excite that relay element in response to said received electromotive forces, and train carried pole changing means including contacts of said twoelement relay. and interposed in said second circuit means to reverse the connection of the second relay element each on period of the received electromotive forces to operate said two-element relay at a code rate corresponding to that of the rail current.

8. In combination, a track section having a normal direction of tramo; trackway means including a source of alternating current and a coder and connected across the rails at the exit end of said section to supply current which flows in the rails in series and which is 'coded to have recurrent on periods, a train to travel said section and having two inductors mounted ahead of its leading pair of wheels with one inductor over each rail for each inductor to receive an alternating electromotive force in response to each on period of said coded current, a train carried two-element alternating current relay, train carried means to connect the two elements of said relay to said inductors and including a-rst and a second transformer, said rst transformer having two primary windings and two secondary windings and said second transformer having two primary windings and a secondary winding, each inductor connected to two of said primary windings, one of each of the transformers, one element of said relay connected to one secondary winding of the first transformer and the other element of the relay connectedvto the other secondary winding of the first transformer in series with the secondary winding of the second transformer, and said two primary windings of the rst transformer additive in respect to electromotive force received by said inductors due to current flowing in the rails in series and said two primary windings of the second transformer opposing in respect to suchelectromotive forces due to current flowing in the rails in series whereby said relay is effectively operated in response to said coded current and false operation of the relay due to foreign current flowingy inthe rails in mitter and said second relay provided with av pick-dpi circuit including a front contact of the code transmitter and a front contact of the irst relay and with a stick circuit including a back contact of the code transmitter whereby said iirst relay is picked up for the odd numbered' on code periods and is released for the even numbered on code periods, a source of alternating current, means including a contact of said code transmitter and pole changing contacts of said first relay to connect said current source across the rails of said section to supply a track circuit current coded at said preselected codeV rate and a reversal of phase with respect to said source of alternating current upon the occurrence of'each on code period, and a train to travel said section provided with signal apparatus disposed in inductive relation tov the rails and eiectively responsive to the energy received from said track circuit current due to said code rate of its on periods and said reversal of phase each on period. lo: In combinatiom'a track section, a code repeater relay'movable to kalternately close front and back contacts and characterized by a predetermined` transfer interval in the movement between the front and back contacts, a source of` alternating current, a iirst circuit including a front contact of said code repeater relay to connect;r said: current Vsource across the rails of said section to supply a track circuit current of normal relative polarity, a second circuit including a back contact of said code repeater relay to connect said current source across the rails of said section to supply a track circuit current of reverse relative polarity, means including a code transmitter to operate said code repeater relay at a preselected code rate to code said track circuit current to haveA alternate on and oi periods corresponding to said code rate with each on periodequal to the interval said front or said back code repeater relay contact; is closed and each oif period equal to said transfer interval, a train to travel said section and provided with signal apparatus disposed in inductive relation to the rails to receive energy in response to said track circuit current and effectively operated due to said code rate of the on periods of the track ycircuit and said reversal of its relative polarity.

11. In combination, a track section, trackway means including a source of alternatinglcurrent connected across the rails of said section to supply current thereto, coding means having contacts interposed in the connection of said current source to the rails and operable at times to code the alternating current .to have alternate on and off periods of a preselected rate and a reversal of phase each on period, a train to travel said section and provided with two inductors one over each rail for each inductor to receive an electromotive force corresponding in code to that of said rail current, a train carried transformer having two primary windings one connected to each of said inductors and two secondary wind-9 ings, a train carried two-element alternating current` relay having one element connected to a; first one of said secondary windings and its other element connected toia second one of said secondary windings for energizing both said. relay elementsA in response to` said received electromotiv-e forces, another train carried relay'con.- nected to said first secondary winding to energize such other relay by the electromotive force created in said iirst secondary winding each on period oi the railV current, and circuit means including a fron-t contact of said other relay and normal and reverse contacts ofV said two-eiement relay to reverse the connectionl oisaidi second secondary winding to cause operation of said two-element relay at a rate corresponding to said' preselected rate. Y

12.1n combination, a track section, trackway means including a source of alternating current connected across the rails of said section to f supply current thereto, coding means having contacts interposed in the connection or' said current source to the rails and operable at times to code the alternating current to have alternate onand ofi periods of a preselected rate and a reversal of phase each on period, a train to travel said section and provided' withv two inductors one over each rail for each inductor to receive an electromotive force corresponding in code to that of said rail current, a train carried transformer having two primary windings one connected to each of said inductors and two secondary windings, a train carried two-element alternating current relay having one element connected to a iirst one of said secondary windings and lits other element connected to a second one of said secondary windings for energizing both said relay elements in response to said received electromotive forces, another train carried relay connected to said iirstsecondary winding to venergize such other relay by the electromotive force created in said first secondary winding each on period of the rail current, and train carried circuit means including contacts controlled in part by said other relay and in part by said two-element relay to pole change the connection of said other relay element to said second secondary winding to reverse the phase of the electromotive force supplied to said other relay element for operating said two-element vrelay at a rate corresponding to said preselected rate.

13. In combination, a track section having a normal. direction of trafc and provided with trackway means connected across the rails at the exit end of the section to supply alternating current that iiows in the rails in series, said trackway means including coding means to code such current to have alternate on and off periods and the current pulses of successive on periods.,

to be of reverse relative polarities, a train to travel said section provided with two inductors mounted ahead of the leading pair of wheels with one inductor over each rail for each inductor to receive an electromotive force of the same code as said rail current, a iirst and a second transformer on said train; each said transformer having a first and a second primary winding, said iirst transformer having a iirst and a second secondary winding and said second transformer having a secondary winding; said first primary windings connected in series to a rst one of said inductors and said second primary windings connected in series to the second one of said inductors, the iirst and second primary windings of the rst transformer disposed to add the electromotive forces received by said inductors duen to said coded series rail current to create a corresponding electromotive force in each of the rst and second secondary windings of the first transformer, said rst and second primary winding of said second transformer disposed to subtract the electromotive forces received by said inductors due l to said coded series rail current, and a train carried two-element relay having one element connected to the rst secondary winding of said first transformer and another element connected to the second secondary winding of the first transformer through the secondary winding of the second transformer and pole changing contacts of the two-element relay to operate such relay in response to said coded rail current and to balance out the energization of the relay due to stray alternating current flowing in the rails in multiple.

14. In combination, a track section having a normal direction of tramo, trackway means including a source of alternating current and a coder and connected across the rails at the exit end of said section to supply to the rails current coded to have alternate on and off periods of a preselected code rate, a train to travel said section and provided with receiving means mounted on the train in inductive relation to said rails to receive an alternating electromotive force in response to each on period of said coded current, a train carried two-element alternating current relay, a flrst circuit means Vto couple a rst element of said relay to said receiving means to energize that element in response to each pulse of said electromotive force, a second circuit means to couple a second element of said` relay to said receiving means to energize that element in response to each pulse of said electromotive force, another relay connected to said rst circuit in multiple with said first relay element to be energized by each pulse of said electromotive force, and contacts of said other relay and said two-element relay interposed in said second circuit means to pole change the `connection of said second relay element upon the occurrence of each pulse of said electromotive force to operate said two element relay at said preselected code rate.

l5. In combination, a circuit which is supplied at times with alternating current coded to have alternate on and off periods of a preselected code rate, a two-element alternating current relay, a rst circuit means to couple a first element of said relay to said circuit to energize that element in response to each pulse of said coded current, a second circuit means to couple a second element of said relay to said circuit to energize that element in response to each ypulse of said coded current; a first, a second and a third relay; means to connect said first relay to said first circuit means to energize said first relay in response to each pulse of said coded current, means including a normal contact of said two-element relay and a front contact of said first relay to energize said second relay, means including a reverse contact of said twoelement relay and a front contact of said rst relay to energize said third relay, and two alternative circuit paths a first one of which includes a normal contact of said two-element relay and a front contact of said second relay and a second one of which paths includes a reverse contact of said two-element relay and a front contact of said thirdrelay, and said two circuit paths included in said second circuit means to pole change the connection of said second relay element to operate said two-element relay at said code rate in response to said coded current.

-PAUL N. MARTIN. 

